This invention relates generally to transparencies useful in electrographic and xerographic imaging and printing processes, and more specifically to transparencies with certain coatings thereover, which transparencies, for example, possess compatibility with toner compositions, and permit improved toner flow in the imaged areas of the transparency thereby enabling images of high quality with no background deposits to be permanently formed thereon. Thus, in one embodiment, the present invention relates to transparencies comprised of a suitable supporting substrate with certain coatings thereover, such as blends of poly(ethylene oxide) with carboxymethyl cellulose, reference U.S. Pat. No. 4,592,954, the disclosure of which is totally incorporated herein by reference; and other coatings as illustrated herein, which transparencies are useful in electrographic and xerographic, imaging and printing processes. Additionally, in another embodiment of the present invention there are provided transparencies useful in electrographic and xerographic imaging systems which transparencies are comprised of a supporting substrate, a first coating of, for example, poly(vinylmethylether), and a second coating thereover of ethyl cellulose, or hydroxypropyl cellulose.
In the formation and development of xerographic images, there is generally applied to a latent image generated on a photoconductive member a toner composition comprised of resin particles and pigment particles. Thereafter, the image is transferred to a suitable substrate, and affixed thereto by, for example, heat, pressure, or a combination thereof. It is also known that transparencies can be selected as a receiver for the transferred developed image originating from the photoconductive member, which transparencies are suitable for selection with commercially available overhead projectors. Generally, these transparent sheets are comprised of thin films of one or more organic resins, such as polyesters, which have the disadvantage in that undesirable poor toner composition adhesion results with such materials.
Many different types of transparencies are known, reference for example U.S. Pat. No. 3,535,112, which illustrates transparencies comprised of a supporting substrate, and polyamide overcoatings. Additionally, there are disclosed in U.S. Pat. No. 3,539,340 transparencies comprised of a supporting substrate and coatings thereover of vinylchloride copolymers. Also known are transparencies with overcoatings of styrene acrylate, or methacrylate ester copolymers, reference U.S. Pat. No. 4,071,362; transparencies with blends of acrylic polymers and vinyl chloride/vinylacetate polymers, as illustrated in U.S. Pat. No. 4,085,245; and transparencies with coatings of hydrophilic colloids as recited in U.S. Pat. No. 4,259,422. Furthermore, there is illustrated in U.S. Pat. Nos. (1) 4,489,122 transparencies with elastomeric polymers overcoated with poly(vinylacetate), or terpolymers of methylmethacrylate, ethyl acrylate, and isobutylacrylate; and (2) 4,526,847 transparencies comprised of overcoatings of nitrocellulose.
With further respect to the prior art, there are illustrated in U.S. Pat. No. 4,370,379 transparencies with, for example, a polyester (Mylar) substrate with a transparent plastic film substrate 2, and an undercoating layer 3 formed on at least one surface of the substrate 2, and a toner receiving layer 4 formed on the undercoated layer, reference column 2, line 44. As coatings for layer 3, there can be utilized the resins as illustrated in column 3, including quaternary ammonium salts, while for layer 4 there are selected thermoplastic resins having a glass transition temperature of from a minus 50 to a minus 150.degree. C., such as acrylic resins, including ethylacrylate, methylmethacrylate, and propyl methacrylate; and acrylic acid, methacrylic acid, maleic acids, and fumaric acid, reference column 4, lines 23 to 65. At line 61 of this patent, there is mentioned that thermoplastic resin binders other than acrylic resins can be selected, such as styrene resins, including polystyrene, and styrene butadiene copolymers, vinyl chloride resins, vinylacetate resins, and solvent soluble linear polyester resins. A similar teaching is present in U.S. Pat. No. 4,480,003 wherein there is disclosed a transparency film comprised of a film base coated with an image receiving layer containing thermoplastic transparent polymethacrylate polymers, reference column 2, line 16, which films are useful in plain paper electrostatic copiers. Other suitable materials for the image receiving layer include polyesters, cellulosics, polyvinyl acetates, and acrylonitrile-butadiene styrene terpolymers, reference column 3, lines 45 to 53. Similar teachings are present in U.S. Pat. No. 4,599,293, wherein there is described a toner transfer film for picking up a toner image from a toner treated surface, and affixing the image, wherein the film consists of a clear transparent base and a layer firmly adhered thereto, which is also clear and transparent, and is comprised of the specific components as detailed in column 2, line 16. Examples of suitable binders for the transparent film that are disclosed in this patent include polymeric or prepolymeric substances, such as styrene polymers, acrylic, and methacrylate ester polymers, styrene butadienes, isoprenes, and the like, reference column 4, lines 7 to 39. The coatings recited in the aforementioned patents contain primarily amorphous polymers which do not undergo the desired softening during the fusing of the xerographic imaging process, and therefore these coatings do not aid in the flow of pigmented toners. This can result in images of low optical density. In contrast with the coatings of the present invention, which include, for example, polymers with a high degree of crystallinity and sharp melting points, there is enabled an increase in toner flow in the imaged areas thus yielding images, especially with mixed colors such as green, black and purple with acceptable optical density values as indicated hereinafter.
Patents of background interest include U.S. Pat. Nos. 3,275,436; 3,854,942; 4,294,422; 4,301,195; 4,419,004; 4,419,005; 4,489,122; and 4,529,650. Also known are thermal transfer imaging sheets containing certain coating compositions thereof, and more specifically processes for obtaining transparencies suitable for the effective transfer of developed images from a donor sheet which comprises providing a transparent substrate, and applying a coating thereto selected from poly(vinylethers), poly(acrylic acids), poly(methacrylic acids esters), reference U.S. Ser. No. 666,702 relating to thermal transfer printing sheets.
Moreover, there are known coatings for ink jet transparencies including blends of carboxylated polymers with poly(alkylene glycol), reference U.S. Pat. No. 4,474,850; transparencies containing blends of poly(vinyl pyrrolidone) with matrix forming polymers such as gelatin or poly(vinyl alcohol), swellable by water and insoluble at room temperature but soluble at elevated temperatures, reference U.S. Pat. No. 4,503,111; and ink jet transparencies comprised of blends of poly(ethylene oxide) with carboxymethyl cellulose as illustrated in U.S. Pat. No. 4,592,954, the disclosure of which is totally incorporated herein by reference.
Although the transparencies illustrated in the prior art are suitable in most instances for their intended purposes, there remains a need for new transparencies with coatings thereover that are useful in electrographic and xerographic imaging processes, and that will enable the formation of images with high optical densities. Additionally, there is a need for transparencies which permit improved toner flow in the imaged areas thereby enabling higher quality transparencies with acceptable optical densities. There is also a need for transparencies with specific coatings that possess other advantages, inclusive of enabling excellent adhesion between the toned image and the transparency or coated papers selected, and wherein images with excellent resolution and no background deposits are obtained.